BG8.7 | Nature-based and Innovative Solutions For Water Quality Challenges
PICO
Nature-based and Innovative Solutions For Water Quality Challenges
Co-organized by HS13
Convener: Hannah WallingECSECS | Co-conveners: Lucy Crockford, Marc Stutter, Lipe Renato Dantas Mendes
PICO
| Fri, 08 May, 16:15–18:00 (CEST)
 
PICO spot 5
Fri, 16:15
Water quality is a critical environmental and societal challenge posing urgent challenges for ecosystems, human health and sustainable development. Anthropogenic drivers such as agricultural intensification, urbanisation, industrial activity and climate change are intensifying pressures on aquatic systems, leading to nutrient enrichment and eutrophication, sediment and contaminant loading, and emerging pollutants. Conventional management approaches are often inadequate, prompting growing recognition of the potential of innovative methods and nature-based solutions to deliver cost-effective, resilient and multifunctional alternatives.
This session provides a platform for research that advances the concepts, design, implementation, and evaluation of solutions to water quality challenges. We welcome contributions on nature-based interventions, integrated catchment management and restoration projects, alongside novel approaches leveraging new technology, modelling and data-driven decision support. Interdisciplinary case studies and work that considers the policy, governance, and community dimensions of implementing these solutions and mainstreaming nature-based solutions are particularly welcome. By bringing together science, practice and policy, the session aims to identify pathways towards more sustainable and inclusive water quality management.

PICO: Fri, 8 May, 16:15–18:00 | PICO spot 5

PICO presentations are given in a hybrid format supported by a Zoom meeting featuring on-site and virtual presentations. The button to access the Zoom meeting appears just before the time block starts.
Chairpersons: Hannah Walling, Lucy Crockford, Marc Stutter
Solutions For Agricultural Water Quality
16:15–16:17
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PICO5.1
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EGU26-15234
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On-site presentation
Lipe Renato Dantas Mendes, Hannah Walling, Philip Schuler, Lucy Crockford, Paul Quinn, Stephanie Terreni-brown, Toby Parkes, Ellie Morris, Mark Wilkinson, and Marc Stutter

Diffuse nutrient pollution from agricultural runoff remains a major pressure on freshwater systems, contributing to eutrophication and downstream ecosystem degradation. Nature-based solutions (NbS) that can be deployed close to source are increasingly sought as cost-effective and multifunctional alternatives to conventional treatment approaches. Mycoremediation, using fungi to transform or retain contaminants, has potential but remains largely untested for promoting nutrient concentration and load reductions in agricultural drainage waters. Through a tiered experimental framework, we evaluate fungal-based filter matrices designed to treat agricultural runoff, with a primary focus on nitrate (NO₃⁻) and phosphate (PO₄³⁻) removal. This presentation focuses on the design, comparative performance, and field evaluation of fungal-based NbS for agricultural drainage treatment.

Filters combine organic and inorganic substrates selected to promote fungal colonisation and sustained biogeochemical activity. Saprotrophic fungal strains originating from England and Scotland were isolated, genetically confirmed, and screened under laboratory conditions to assess nutrient uptake performance. Column experiments enabled the shortlisting of substrate–fungal combinations with the strongest nutrient removal potential. Selected combinations were then tested in channel-scale experiments simulating agricultural drainage conditions using water enriched with NO₃⁻ and PO₄³⁻. We quantify upstream and downstream nutrient concentrations, dissolved oxygen dynamics, and redox potential within the filter media to assess conditions conducive to denitrification and nutrient retention. In parallel, continuous water quality monitoring is being used to assess filter performance under real-world hydrological and chemical variability across multiple agricultural sites in England and Scotland.

Data collection is ongoing and results are not yet conclusive; however, the combined laboratory, mesocosm, and field datasets will provide a robust evaluation of mycoremediation filters as scalable NbS for mitigating diffuse agricultural nutrient pollution.

How to cite: Dantas Mendes, L. R., Walling, H., Schuler, P., Crockford, L., Quinn, P., Terreni-brown, S., Parkes, T., Morris, E., Wilkinson, M., and Stutter, M.: Evaluating fungal-based nature-based solutions for agricultural drainage treatment, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15234, https://doi.org/10.5194/egusphere-egu26-15234, 2026.

16:17–16:19
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PICO5.2
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EGU26-19236
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ECS
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On-site presentation
Iñigo Barberena, Rafael Muñoz-Carpena, Miguel Ángel Campo-Bescós, and Javier Casalí

Effective management of agricultural runoff is essential to safeguard water quality and promote sustainable land use. Vegetative filter strips (VFS), areas of dense vegetation established between pollution sources and receiving surface waters, are widely implemented as a nature-based solution to mitigate nutrient and sediment export from agricultural fields. Their performance is commonly assessed using established computer models such as VFSMOD. While VFSMOD provides a robust, physically-based representation of VFS performance, its conventional application is largely deterministic, limiting its ability to address the intrinsic environmental variability and uncertainty on VFS design for environmental management.

This work presents a new computational tool consisting of a graphical user interface built upon VFSMOD, specifically developed to enhance the design and assessment of vegetative filter strips under variable conditions. The cross-platform tool extends VFSMOD by incorporating a hypothesis-testing framework for model calibration based on observational data. Once calibration is achieved, the tool supports an advanced VFS design phase in which input uncertainty is considered and mitigation performance in terms of both efficiency and reliability.

The methodology was applied to a real-world agricultural setting. The case study demonstrates how the proposed tool facilitates robust VFS design while explicitly accounting for input uncertainty. Results indicate improved decision support compared with the previous user interface used to run VFSMOD.

 

How to cite: Barberena, I., Muñoz-Carpena, R., Campo-Bescós, M. Á., and Casalí, J.: An Integrated Computational Framework for the Advanced Design of Vegetated Filter Strips in Agricultural Landscapes, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19236, https://doi.org/10.5194/egusphere-egu26-19236, 2026.

16:19–16:21
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PICO5.3
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EGU26-14890
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On-site presentation
Wetland restoration for water and wallets
(withdrawn)
Nandita Basu and Kim Van Meter
16:21–16:23
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PICO5.4
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EGU26-13324
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ECS
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On-site presentation
Fulu Zhuang, Simon Harrison, Martha Gosch, and William Burchill

Point source pollution from farmyard runoff can be a significant pressure on surface water quality in agricultural catchments with large uncertainty around the extent of these losses between farms and across seasons. Targeted natural-based solutions, such as willow filter beds and bunded drain systems, are currently being funded and deployed on Irish farms to intercept contaminated farmyard runoff before it enters receiving waters. However, field-based evidence of their effectiveness under variable farm management and hydrological conditions is limited.

This study presents an ongoing monitoring program aimed at (1) characterizing the physio-chemical characteristics of farmyard runoff across different farms and seasons and (2) evaluating the mitigation performance of small-scale willow filter beds (n = 6) and bunded drains (n = 2) installed on Irish farms in 2025. Water sampling consisted of monthly grab samples collected at the mitigation system inlets, internal treatment cells, and outlets, and was analyzed for pH, electrical conductivity (EC), dissolved oxygen (DO), total suspended solids (TSS), and nitrogen and phosphorus species. Sampling at the inlets allowed for the determination of physio-chemical parameters of farmyard runoff, which were also compared to the outlet values to determine the effectiveness of the mitigation systems. This abstract focuses on pH, EC, DO, and TSS data collected during the initial monitoring period from October to December 2025. Initial nitrogen and phosphorus concentration samples are currently under analysis and will be presented at the conference.

Preliminary observations indicate pronounced temporal variability in the composition of farmyard runoff, particularly in response to variability in farmyard runoff flow rates. Across the monitored farms and three sampling dates, inlet water quality exhibited substantial variability, with mean (Min-Max) TSS concentrations of approximately 120 mg L-1 (4-320 mg L-1), pH of 7.2 ( 5.3-9.2), EC of 900 µS cm-1 ( 40-1860 µS cm-1), and DO concentrations of 6 mg L-1 ( 0.2-11.3 mg L-1).

Early-stage analysis suggests attenuation of suspended sediment across the mitigation systems, with mean (Min-Max) outlet TSS concentrations of 60 mg L-1 ( 0.4-174 mg L-1), generally lower than those observed at the inlets. This reduction is accompanied by a reduction of the EC at the outlets to a mean (Min-Max) of 450 µS cm-1 (118-1074 µS cm-1). These patterns were most apparent during periods when flow conditions were sufficient to generate outlet discharge, enabling the comparison between inlets and outlets.

This study will continue for two years to encompass a wider range of seasonal dynamics, farmyard management conditions and additional water quality parameters, enabling a more comprehensive evaluation of farmyard runoff composition and mitigation effectiveness of these nature-based solutions as they mature.

How to cite: Zhuang, F., Harrison, S., Gosch, M., and Burchill, W.: Evaluation of the effectiveness of nature-based solutions to reduce the impact on water quality of farmyard runoff , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13324, https://doi.org/10.5194/egusphere-egu26-13324, 2026.

16:23–16:25
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PICO5.5
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EGU26-23225
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ECS
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On-site presentation
Irene Biliani and Ierotheos Zacharias

In recent decades, eutrophication, caused by the enrichment of nutrients in the water bodies
(mostly due to N and P), has emerged as a global environmental challenge with far-reaching
consequences for aquatic ecosystems health. ZeoPhos, an innovative eco-friendly clay-based
material, promises to simultaneously adsorb ammonium and orthophosphate ions, causing
eutrophication, from natural freshwaters. ZeoPhos consists of natural zeolite with a synergistic
combination of iron, calcium, and humic ions to enhance nutrient-binding affinity. Material
characterisation analysis (such as SEM/EDS and TEM) confirms that ZeoPhos successfully
altered the surface morphology and elemental composition, creating a more reactive surface for
adsorption. Batch adsorption kinetic experiments demonstrated high efficiency at achieving
removal rates of 78% and 70% for ammonium and orthophosphate ions, respectively. Pseudo-
second-order model of the kinetic studies suggests that the removal process is governed by
chemisorption, while the Langmuir model of isotherm studies indicate monolayer adsorption
onto a finite number of sites. The maximum adsorption capacities were 28.61mg/g and
27.13mg/g for ammonium and orthophosphate ions, respectively. ZeoPhos is an innovative,
economic and eco-friendly adsorbent material of high-capacity, capable of dual-nutrient
adsorption and ultimately promising to mitigate eutrophication in freshwater bodies.

How to cite: Biliani, I. and Zacharias, I.: Dual-nutrient removal from eutrophic freshwater using ZeoPhos: Synthesis, characterization, and adsorption mechanisms of a multi-ion modified zeolite., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-23225, https://doi.org/10.5194/egusphere-egu26-23225, 2026.

16:25–16:27
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PICO5.6
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EGU26-2048
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ECS
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On-site presentation
Abhishek Kumar Chaubey and Dinesh Mohan

Emerging contaminants, such as pharmaceutical residues, in aqueous environments provide serious threats to public health, aquatic life, and deteriorate water quality, demanding long-term and economical remediation techniques. These drugs are frequently used all around the world, and high residual concentrations are reported in wastewater across continents, including Asia. Biochar has drawn more attention as an adsorbent due to its high stability, surface functional groups, and potential for surface modification. In this study, biochar derived from rice husk was modified using the co-precipitation method to enhance acetaminophen and trimethoprim adsorption. Engineered biochar (surface area = 419 m2/g) easily adsorbed aqueous acetaminophen and trimethoprim (∼8 h equilibrium time) with adsorption capacities of 69.7–137.4 mg/g and 54.2–269 mg/g, respectively, vs. pristine biochar (surface area = 182 m2/g). The Elovich kinetic model (R2 = 0.90-0.99) showed the best correlation for both acetaminophen and trimethoprim. All isotherm models gave R2 > 0.95, suggesting simultaneous sorption processes (monolayer/multilayer and homogeneous/heterogeneous) are taking place. Mg or Al leaching from the adsorbent is well within the drinking water limit and not a concern. Spent adsorbent was regenerated using EDTA, HCl, H₂SO₄, ethanol, and methanol. Potential sorption interactions were hydrogen bonding, pore diffusion, π-π interaction, and electrostatic interactions. These findings demonstrate the potential of engineered biochar as a versatile and sustainable water treatment. The study contributes to advancing green materials for environmental remediation and provides insights for scaling biochar technologies within circular-economy frameworks.

How to cite: Chaubey, A. K. and Mohan, D.: Valorization of Rice Husk into MgO/Al₂O₃-Modified Biochar for Remediating Aqueous Emerging Contaminants , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2048, https://doi.org/10.5194/egusphere-egu26-2048, 2026.

16:27–16:37
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PICO5.7
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EGU26-21826
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ECS
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solicited
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On-site presentation
Katherine Molloy and Valerie McCarthy

Dissolved organic matter (DOM) is found across all freshwater systems and originates from soils, leaf litter and leachate from plant material and the decomposition processes. However, as a consequence of a combination of changes in both land use practices and climate change there has been a recorded increase in DOM export in freshwater systems over the last number of years. High concentrations of Dissolved Organic Matter (DOM) in water react with chlorine during treatment, forming harmful disinfection by-products (DBPs) such as trihalomethanes (THMs) and chloroform. There are numerous options available to mitigate and treat DBPs as part of the water treatment process, including a range of technologies and management procedures which aim to reduce contact between DOM precursors and disinfectants. Nevertheless, protection of the water at source represents an alternative and likely additional activity which could act to reduce DBP formation in drinking water in a more cost effective and efficient way.

Source Water Protection (SWP) through the use of Nature Based Solutions and other methodologies has been widely implemented in many regions of the world to improve raw water quality. However, compared with other potential contaminants such as microbial pathogens, very little work has specifically focused on the reduction of DOM input to water treatment plants. This study examines the potential effectiveness of SWP measures at reducing organic matter with the aim of minimising human exposure to DBPs in drinking water. A review was undertaken to identify SWP measures considered most likely to mitigate against DOM, pinpointing five key land use categories linked to DOM loading: forestry, peatland, agriculture, lakes/reservoirs, and wastewater treatment. Measures were assessed based on their proven effectiveness at reducing DOM or other relevant pollutants. Input was gathered from the Irish water sector via a focus group and survey to evaluate the feasibility of implementing these measures at catchment scale. The findings suggest there is a potential role for SWP for the mitigation of DOM in source water leading to improved DBP management in conjunction with treatment plant improvements and upgrades. However, there is currently a lack of evidence-based research demonstrating the effectiveness of SWP measures in mitigating against DOM and DBP formation which is a significant barrier to the uptake and implementation of such measures. In addition, active and participatory approaches to education and support in this area will encourage stakeholders to shift their perception from an end of pipe only solution to a multi-barrier approach to reduce the overall risk of DBP contamination of drinking water.

 

How to cite: Molloy, K. and McCarthy, V.: Potential source water protection measures to mitigate against organic matter based on its pathway and process of contamination using Ireland as a case study., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21826, https://doi.org/10.5194/egusphere-egu26-21826, 2026.

16:37–16:39
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PICO5.8
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EGU26-21152
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ECS
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Highlight
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On-site presentation
Hannah Walling, Lipe Renato Dantas Mendes, Lucy Crockford, Ellie Morris, Toby Parkes, Philip Schuler, Marc Stutter, Mark Wilkinson, and Stephanie Terreni-Brown

Water quality management in agricultural catchments remains a critical environmental and societal challenge. Whilst nature-based solutions (NbS), such as mycoremediation (the use of fungi to remediate contamination and remove pollutants) offer potentially resilient alternatives to conventional approaches, their widespread adoption is often constrained by social, practical and governance barriers. 

 

This presentation explores the role of stakeholder engagement in shaping the design, implementation, and upscaling of fungal-based filtration systems developed to intercept agricultural runoff at source. Building on ongoing field trials of mycoremediation filters, primarily targeting nitrate (NO₃⁻) and phosphate (PO₄³⁻) removal, we employed mixed-methods engagement framework to compliment practical results found in the field. Participants included a range of experienced practitioners, including farmers, land managers and regulators. 

 

Engagement activities helped identify perceived benefits and risks of filter deployment, practical constraints related to land use, regulations, maintenance and costs, and opportunities for interaction with existing farm infrastructure and agri-environmental schemes. Coupling stakeholder-derived insights and iterative in-field testing of filter design is refining the research to prioritise environmentally effective and operationally feasible solutions. This work demonstrates how integrating social and environmental evidence can support the transition of NbS from experimental trials, to scalable, catchment-scale interventions, contributing to more inclusive and sustainable water quality management. 

 

How to cite: Walling, H., Renato Dantas Mendes, L., Crockford, L., Morris, E., Parkes, T., Schuler, P., Stutter, M., Wilkinson, M., and Terreni-Brown, S.: Integrating social and environmental evidence to support the development of effective fungal-based filters for agricultural water remediation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21152, https://doi.org/10.5194/egusphere-egu26-21152, 2026.

16:39–16:41
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PICO5.9
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EGU26-22099
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ECS
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On-site presentation
Tamara Vobruba, Marco Hartl, Cecilia Delgado, Günter Langergraber, Verena Germann, and Ines Costa- Pereirae

Resource-oriented sanitation (ROS) is increasingly discussed as an innovative approach for circular resource use, yet its cross-sectoral sustainability implications are rarely assessed at the level of specific Sustainable Development Goal (SDG) targets. An expert-based scoring approach adapted from Nilsson et al. (2016) was applied within the Austrian UniNEtZ project to assess interactions between ROS and 123 SDG targets. The analysis identified 42 non-neutral interactions, particularly related to water management, nutrient cycling, food production, resource efficiency, health, innovation, and governance. ROS has the potential to improve water quality and reduce pollution loads through direct sanitation pathways as well as indirect effects linked to the reuse of reclaimed water and nutrients, with decentralised and nature-based solutions representing important implementation pathways. The identified interactions were contextualised through a food-system perspective to examine cross-sectoral pathways relevant for integrated governance and policy-relevant sustainability assessment in infrastructure-mature contexts.

How to cite: Vobruba, T., Hartl, M., Delgado, C., Langergraber, G., Germann, V., and Costa- Pereirae, I.: Resource-oriented sanitation and the SDGs: a target-level interaction assessment in the Austrian context, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22099, https://doi.org/10.5194/egusphere-egu26-22099, 2026.

Solutions For Wastewater Treatment
16:41–16:43
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PICO5.10
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EGU26-8744
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ECS
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On-site presentation
Dongjun Seo, Jaechul Yi, Jaeyun Jung, Hyejoo Yoon, Jiyoun Kim, Gi Seok Kwon, and Hee Deung Park

Abstract

Continuous accumulation of sludge in septic tank systems causes reduced treatment efficiency and increased maintenance costs. However, existing Activated Sludge Models (ASM) are limited to bacterial trophic levels, failing to quantitatively explain sludge reduction mechanisms driven by higher-level predators. This study proposes a novel extended model integrating the ecological dynamics of rotifers and ciliates, based on the Storage-Growth framework of ASM3. The model functionally divides the bacterial community into Bacteria Biomass (XB) and Filamentous Biomass (XFB), and incorporates ciliates (XP) and rotifers (XR) that selectively graze on them, comprising a total of 16 state variables and 13 processes. Specifically, the model mathematically structures predator grazing not merely as biomass conversion, but as a process mediated by internal storage products (XSTO) involving respiration and maintenance metabolism during famine conditions. Differential analysis of Total Suspended Solids (XSS) demonstrated that, in addition to conventional endogenous respiration, the additional carbon mineralization occuring at the predation stage is a key mechanism for sludge reduction. Furthermore, the model suggests the potential for controlling sludge bulking through rotifer predation on filamentous bacteria. By introducing ecological interactions into process modeling, this study provides an advanced quantitative framework capable of simultaneously predicting sludge reduction efficiency and operational stability in septic tanks.

Acknowledgements

Following are results of a study on the "Convergence and Open Sharing System" Project, supported by the Ministry of Education and National Research Foundation of Korea

How to cite: Seo, D., Yi, J., Jung, J., Yoon, H., Kim, J., Kwon, G. S., and Park, H. D.: Development of an extended ASM framework integrating rotifer–ciliate ecological mechanisms for predicting sludge reduction in septic tank systems, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8744, https://doi.org/10.5194/egusphere-egu26-8744, 2026.

16:43–16:45
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PICO5.11
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EGU26-9302
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ECS
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On-site presentation
Styliani Biliani and Ioannis Manariotis

The scope of this study was to evaluate different environmental factors that affect the ability of algal-bacteria consortia to remove nutrients. The dark-cycle nitrogen removal process was investigated, providing valuable insights for improving wastewater treatment systems. The behavior of the consortia was examined under various illumination regimes (continuous 24-h light and a 12:12 h light-dark cycle) and varying aeration conditions (0 to 12 h and 0 to 24 h of air supply). Continuous light exposure combined with continuous aeration resulted in the highest nitrate and phosphorus removal. The results indicated that light duration had a greater effect on nutrient removal than air supply. When light and aeration were stopped after 12 hours, the zero‑order removal rate constants during the dark period decreased by 36% for nitrates and 55% for phosphorus compared with the 24‑hour light and aeration condition. Nitrate removal occurred more rapidly than phosphorus removal in the light and slightly faster in the dark. Although nutrient removal during the dark phase decreased approximately 58% for nitrates and 45% for phosphorus relative to the light phase, it did not cease entirely, even when the culture was refed without additional aeration. These findings demonstrate that algal-bacteria consortia can efficiently remove nitrates and phosphorus from wastewater, even in the absence of light, offering important information for the design and optimization of outdoor algal-based wastewater treatment systems.

How to cite: Biliani, S. and Manariotis, I.: Nutrient Removal in Algal-Bacterial Consortia Treating Secondary Effluent During Light-Dark Cycles, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9302, https://doi.org/10.5194/egusphere-egu26-9302, 2026.

16:45–16:47
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PICO5.12
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EGU26-14095
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ECS
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On-site presentation
Suman Acharya, Raymond Wilson, Gabriel Gaffney, Chris Johnston, and Phil Jordan

Phosphorus (P) discharge from sewage treatment works remains a significant source of P pollution in freshwater systems. While a wide range of P-removal technologies have been successfully implemented at large wastewater treatment works (WWTWs), their application in small-scale systems is often constrained by high capital and operational costs, technical complexity, and highly variable influent flows. Consequently, P releases from small treatment works can have disproportionate and localised impacts on receiving freshwaters, leading to severe ecological degradation. These impacts are likely to intensify under climate change, particularly during prolonged dry periods associated with low or zero-flow conditions given reduced or zero discharge dilution. Nature-based solutions offer a potential treatment option for P removal in small-scale systems while delivering additional environmental benefits. However, the suitability of these approaches has not yet been extensively studied. Therefore, this study evaluated the performance and applicability of zero-discharge willow biofiltration system for attenuating P discharged from two small-scale WWTWs in Ireland. The experimental design comprised approximately 1.5 ha of mixed variety willow plantation at each site, irrigated with primary-treated wastewater using automated, sequential time-dosed irrigation systems. Using a before-after approach, stream P concentrations, measured as soluble reactive phosphorus (SRP), were monitored upstream and downstream of WWTW discharge points using automated samplers with hourly sampling over a period of 24 hours. Sampling was conducted following three rain-free days each month between March and November over different years. The results showed that, prior to wastewater diversion to irrigate the willow plantation, downstream SRP concentrations were substantially higher than upstream concentrations at both sites, with the highest concentrations observed during the summer months. Following the diversion of wastewater, the difference in SRP concentrations between upstream and downstream sites became negligible, indicating more than 95% of P attenuated through the willow biofiltration system. Ongoing work includes studying the fate of irrigated P to evaluate soil P saturation and P uptake in biomass.   

 

Keywords: Short rotation willow coppice, Effluent, Phosphorus, Wastewater treatment works

How to cite: Acharya, S., Wilson, R., Gaffney, G., Johnston, C., and Jordan, P.: Evaluating the efficacy of short rotation willow coppice in attenuating phosphorus from small-scale wastewater treatment works’ effluent, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14095, https://doi.org/10.5194/egusphere-egu26-14095, 2026.

16:47–16:49
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PICO5.13
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EGU26-20597
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ECS
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On-site presentation
Laura Escarmena, Núria Roca, Sílvia Poblador, Stefania Mattana, Àngela Ribas, Santi Sabaté, Teresa Sauras-Yera, Jenny Solís-Llerena, and Francesc Sabater

Wastewater treatment plant (WWTP) effluent discharge is one of the main pressures in Mediterranean non-perennial streams because of their low dilution capacity. The concentration of nutrients present in effluents leads to the aggravation of the quality of those ecosystems. As an alternative discharge approach, a Mediterranean riparian zone has been used as a nature-based solution (NbS) to remove nitrogen from NH4-rich effluents (3 mg/L). The effluent was discharged through an intermittent horizontal subsurface flow across a 250 m2 riparian soil area located in a Mediterranean basin. The system operated during spring and summer of 2021 and 2023. Effluent application periods (wet conditions) alternated with drainage periods (dry conditions) at a 1:1 ratio.

We conducted sampling campaigns under both conditions and compared them with a control zone. We assessed the removal efficiency of NH4 and NO3 and the impact of the discharge on their concentrations in soil and groundwater. We also measured the N2O soil emissions along with the expression (mRNA) of key microbial functional genes related to nitrification (archaeal and bacterial amoA) and denitrification (nirK and nosZ).

We found mean removal efficiencies of 50% for NH4 and 23% for NO3, similar to those reported for other NbS such as constructed wetlands. As expected, NH4 increased in both groundwater and soil, while NO3 decreased, with concentrations varying between wet and dry periods. Effluent application triggered a significant increase in N2O emissions, also showed a spatial pattern across the riparian zone. The hillslope zone -where the NH4 rich effluent was applied- presented the highest emissions mainly linked to nitrification. The near‑stream zone, characterized by higher soil moisture, had the lowest emissions, consistent with conditions favoring denitrification. Gene expression patterns confirmed the coupling between both processes. Under wet conditions, we found significant positive correlations between N2O and archaeal amoA expression, as well as with nitrifiers/denitrifiers ratio, suggesting that N2O production was more strongly influenced by nitrification. Moreover, we found positive correlations between amoA and nirK genes. The negative correlation between N2O and nosZ/nirK ratio, in addition to high nosZ/nirK ratio values, indicated that wetter conditions favored complete denitrification. Nevertheless, resulting emissions were generally one order of magnitude lower than those of other NbS and like those of riparian zones.

Overall, the biogeochemical heterogeneity of riparian soils, combined with flow intermittency and the NH4 load from wastewater, enhanced both nitrification and denitrification. This resulted in an effective system for nitrogen removal.

How to cite: Escarmena, L., Roca, N., Poblador, S., Mattana, S., Ribas, À., Sabaté, S., Sauras-Yera, T., Solís-Llerena, J., and Sabater, F.: Nitrogen dynamics and removal within a riparian zone used as a nature-based solution for secondary-treated wastewater, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20597, https://doi.org/10.5194/egusphere-egu26-20597, 2026.

16:49–16:51
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PICO5.14
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EGU26-16103
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ECS
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On-site presentation
Kyra Selina Hagge, Poonam Arora, Gregory Howard, and Stephen Moysey

In many human–environment systems, individual actions influence community behavior and environmental outcomes and can be characterized as social dilemmas. In regional wastewater management, decisions made at the household level, such as the choice between individual septic systems and community-scale treatment options like cluster septic systems, collectively shape water quality outcomes at the watershed scale. While innovative wastewater technologies can reduce nutrient and contaminant loads, their effectiveness ultimately depends on adoption and appropriate use by households and communities.

Using a large-scale survey that includes a stated preference experiment conducted in the United States, with a focus on North Carolina (N = 2,068), we examine how willingness to pay (WTP) for improved wastewater treatment technologies varies depending on how individuals conceptualize the underlying interdependent decision context. We classify respondents’ decision-making into four archetypal mixed-motive games: Maximum Difference, Assurance, Chicken, and Prisoner’s Dilemma, and analyze differences in WTP across these mental representations. Results show that respondents, on average, favor individual solutions (advanced septic systems) over collective solutions (cluster septic systems) and are willing to pay a premium for the individual option. We interpret this premium as the cost of cooperation, reflecting perceived risks and governance challenges associated with collective wastewater management. As nature-based technologies and other alternative approaches rely on human cooperation on multiple levels, our findings provide valuable behavioral context for design and implementation of innovative water quality interventions. 

How to cite: Hagge, K. S., Arora, P., Howard, G., and Moysey, S.: When Wastewater Is a Social Dilemma: Individual and Collective Choices in Technology Adoption, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16103, https://doi.org/10.5194/egusphere-egu26-16103, 2026.

16:51–18:00
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